Motor-pump assembly

ABSTRACT

The present invention relates to a motor-and-pump assembly including an electric motor and a piston pump, in particular for slip-controlled brake systems of automotive vehicles, wherein pistons of the pump are adapted to be driven by way of an eccentric, and the drive shaft of the electric motor and a support axle of the piston pump are separately designed, and wherein a three-ring bearing furnished with an eccentric intermediate ring is arranged on the support axle. According to the present invention, at least one counterbalance weight is provided in the proximity of the eccentric for the purpose of noise reduction and enhanced truth of running of the assembly.

TECHNICAL FIELD

The present invention generally relates to motor and pump assemblies andmore particularly relates to a motor-and-pump assembly having reducedvibration characteristics.

BACKGROUND OF THE INVENTION

German published patent application DE 196 32 167 A1 discloses a genericassembly which comprises an electric motor and a piston pump that areappropriate e.g. for use in an ABS (anti-lock system), TCS (tractionslip control) or ESP (Electronic Stability Program) system of acontrolled vehicle brake, and pistons of the pump are drivable by way ofan eccentric. In this publication, a drive shaft of the electric motorand a support axle of the piston pump have a separate design. Further, athree-ring bearing having an eccentric intermediate ring is arranged onthe support axle. However, the eccentric intermediate ring has an unevenmass distribution so that an unbalance will occur when an eccentric ofthis type is used in a motor-and-pump assembly. The unbalance willproduce undesirable noises during operation and load the respectivebearings and the support axle and the pump housing in which the supportaxle is arranged to a major degree.

In view of the above, an object of the present invention is to improveupon an assembly of the type referred to hereinabove so that simpleprovisions permit reducing the unbalance and, thus, achieving anenhanced quietness in operation and reduced load on the bearings or thesupport axle and the pump housing.

According to the p resent invention, this object is achieved in that ina generic motor-and-pump assembly, at least one counterbalance weight isadditionally provided in the proximity of the eccentric.

Preferably, the counterbalance weight is connected directly to the driveshaft or by the intermediary of a sleeve.

Advantageously, the counterbalance weight may be designed integrallywith the intermediate ring.

As an alternative, however, the counterbalance weight may also beconnected to the intermediate ring by way of the sleeve.

Preferably, the counterbalance weight is sintered and, hence, especiallyeasy and simple to manufacture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a motor-and-pumpassembly known from the state of the art.

FIG. 2 is a sectional view of a first embodiment of the assembly of thepresent invention.

FIG. 3 is a second embodiment of the assembly of the present invention,also in cross-section.

FIG. 4 shows a third embodiment of the assembly of the presentinvention.

FIG. 5 shows another embodiment of the motor-and-pump assembly of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the embodiment of FIG. 1 which shows a prior-art motor-and-pumpassembly, an electric motor is designated by reference numeral 1 and apiston pump by reference numeral 2. In the housing 3 of the electricmotor 1, a drive shaft 4 on which a rotor 5 is arranged is mounted in anupper first bearing 6 and a lower second bearing 7 so as to be rotatablerelative to a stator 8. The bearings 6 and 7 are designed as slidingbearings in this example. Secured in the housing 9 of the pump 2 is asupport axle 10 on which an eccentric bearing 11 is arranged. A torquetransmitting sleeve 12 connected to the drive shaft 4 transmits a torquefrom the shaft 4 to an eccentric 13 bearing designed as an intermediatering, whereby pistons 14 of the pump are reciprocating radially relativeto the drive shaft 4 and thereby build up the pressure which is e.g.required for the operation of an ABS (anti-lock system), TSC (tractionslip control) or ESP (Electronic Stability Program) system of acontrolled vehicle brake. The developing reaction forces are conducteddirectly to the support axle 10 and, hence, into the housing 9 of thepiston pump 2 by way of an outer ring 15 of the eccentric bearing 11 andneedle rows.

As mentioned hereinabove, the eccentric 13 designed as intermediate ringexhibits an uneven mass distribution. Therefore, an unbalance isencountered with the use of such an eccentric 13 or eccentric bearing 11in a motor-and-pump assembly, especially due to the large outsidediameter of the eccentric 13. This unbalance causes undesirable noisesin operation, and the respective bearings 6 and 7 and, in particular,the support axle 10 and the pump housing 2, in which the support axle 10is arranged, are loaded to a very great degree.

The embodiments of the present invention illustrated in FIGS. 2 to 5relate to an above-described motor-and-pump assembly so that in eachcase the description of FIG. 1 in its full contents is referred to. Likereference numerals describe identical or at least similar components.

FIG. 2 shows a first embodiment of the present invention wherein acounterbalance weight 18 for compensation of the unbalance produced bythe eccentric 13 designed as intermediate ring is arranged close to theeccentric 13. This ensures both a dynamic and a static balancing with ahigh quality. The eccentric 13 has a simple design, i.e., withoutspecial projections, extensions, etc. An outer ring 15 which representsa counterbearing for the pistons 14 is moved on the eccentric 13 by wayof outside needles. Inside needles 16 of the eccentric bearing 11 moveon the inside on the support axle 10 and on the outside surface in asleeve 17 which is preferably made by drawing or deepdrawing. The torquetransmission from the drive shaft 4 is preferably done by way of pressfit connections between the shaft 4 and the sleeve 17 or between thesleeve 17 and the eccentric 13. Unbalances of the bearing and theeccentric 13 are compensated by means of a counterbalance weight 18which can be sintered in particular. Preferably, the counterbalanceweight 18 is equally connected to the sleeve 17 by a press fit. Thisespecially supports in the connection between the sleeve 17 and thedrive shaft 4. The counterbalance weight 18 has preferably a simpleshape and is therefore easy and inexpensive to manufacture.

FIG. 3 shows a second embodiment of the present invention incross-section. In this embodiment, the counterbalance weight 19 isintegrally designed with the eccentric 13 designed as intermediate ring.Beside the sleeve 17 which has already been mentioned with respect toFIG. 2, there is another sleeve 20 on which the outer ring 15 or theeccentric bearing 11 is moved. Further sleeve 20 is advantageously pressfitted on the eccentric 13. In this arrangement, sleeve 20 on one endmay be provided with a projection so that it additionally fixes theeccentric bearing 15 in an axial direction relative to the drive shaft 4or the support axle 10.

FIG. 4 depicts a cross-section of another embodiment of the presentinvention. According to this invention, at least one counterbalanceweight 21 is provided close to the eccentric 13 and, in this embodiment,is press fitted directly on the drive shaft 4 and, thus, advantageously,can be designed or mounted irrespective of the eccentric 13. The driveshaft 4 and the eccentric 13 designed as intermediate ring areinterconnected by means of an especially welded sleeve 22 in thisembodiment. The axial start of run for the inner and outer bearing ofthe eccentric 13 in the direction of the pump housing 9 is effectedespecially by the intermediary of a metal sheet 23 which is connected,preferably welded, to the intermediate ring 13. The metal sheet 23prevents the eccentric 13 from striking against the pump housing 9 andwearing off.

FIG. 5 shows another and preferred embodiment of the present inventionin a cross-sectional view. Similar to FIG. 3, a counterbalance weight 24is designed integrally with the eccentric designed as intermediate ring13. The counterbalance weight 24 has slightly less favorable propertieswith respect to the dynamic balancing, however, it is considerablyeasier to make than the counterbalance weight 19 of FIG. 3. Apart fromthe sleeve 17, there is another sleeve 20 on which, by way of theoutside needles, the outer ring 15 or the counterbearing is moved. Inthis embodiment, the sleeve 20 is on both ends provided withrespectively one radially outwards directed projection so that it fixesadditionally the eccentric bearing 11 in an axial direction with respectto the drive shaft 4 or the support axle 10. In order to achieve greaterease of assembly of the eccentric bearing 11, the sleeve 20 in thisembodiment has a bipartite design. Equally for the axial fixation of theinside needles 16, the sleeve 17 may include inwards directedprojections at its ends.

Start of the electric motor 1 and, thus, of the drive shaft 4 may befollowed by an axial displacement of the drive shaft 4 in the directionof the support axle 10, as is illustrated in the left-hand half of FIG.5. To reduce the wear and the friction which is produced, thecorresponding end 25 of the support axle 10 may have a rounded design.This is possible in all embodiments of the present invention.

What is claimed is:
 1. Motor and pump assembly, comprising: a motorhaving a drive shaft, a support axle, a torque transmitting sleevecoupled between said motor drive shaft and said support axle, aneccentric bearing coupled to said support axle, wherein an end portionof said support axle is rounded to reduce a frictional loss between saidrounded end portion of said support axle and said motor drive shaft, apiston coupled to said eccentric bearing, a counter balance coupled toat least one of the motor drive shaft, torque transmitting sleeve, orsaid eccentric bearing.
 2. The motor and pump assembly of claim 1,wherein said eccentric bearing includes an eccentric which isfrictionally engaged to said torque transmitting sleeve and wherein saidcounter balance is directly frictionally engaged to said torquetransmitting sleeve.
 3. The motor and pump assembly of claim 1, whereinsaid counterbalance is designed integrally with an eccentric portion ofsaid eccentric bearing.
 4. The motor and pump assembly of claim 1,wherein said counter balance directly frictionally engages the driveshaft of the motor.
 5. The motor and pump assembly of claim 4, whereinsaid counterbalance is designed integrally with an eccentric portion ofsaid eccentric bearing and also designed integrally with said torquetransmitting sleeve.
 6. The motor and pump assembly of claim 1, whereinsaid counterbalance is fabricated from sintered material.